Fan

ABSTRACT

A blower fan includes a lower plate portion made of a material having a thermal conductivity of 1.0 W/(m·K) or more, and a side wall portion made of a material having a thermal conductivity of 1.0 W/(m·K) or more. An upper plate portion arranged to cover an upper side of the impeller includes an air inlet. The upper plate portion, the side wall portion, and the lower plate portion are arranged to together define an air outlet on the lateral side of the impeller. The blower fan further includes a heat source contact portion with which a heat source is to be in contact, the heat source contact portion being arranged in a surface of the blower fan which faces away from the impeller. The heat source contact portion and the tongue portion are arranged to at least partially overlap with each other in the plan view.

1-1. CROSS-REFERENCE TO RELATED APPLICATION

The application is a Continuation of U.S. patent application Ser. No.14/499,680, filed on Sep. 29, 2014, which is based on Japanese priorityapplication No. 2014-004557 filed on Jan. 14, 2014, the entire contentsof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a blower fan.

2. Description of the Related Art

Electronic devices, such as notebook PCs, produce a large amount of heatat CPUs and the like inside cases thereof. This makes it important totake measures against the heat. One common measure against the heat isto install blower fans inside the cases to discharge the heat.

In recent years, electronic devices have been becoming more and moresophisticated in functionality, accompanied by a considerable increasein the temperature inside the electronic devices. Accordingly, there isa demand for a blower fan which is excellent in cooling capability, withthe view of cooling an interior of such an electronic device. A fan unitdisclosed in JP-A 2001-111277 is arranged to discharge an air through anair outlet arranged radially outside blades so that the air can be blownto a heat-radiating component mounted on a circuit board arrangedradially outside the blades. The heat-radiating component is thusdirectly cooled.

However, in recent years, electronic devices have been becoming more andmore densely packed with electronic components, and heat may not besufficiently discharged out of such a recent electronic device only byblowing an air to a heat source.

The present invention has been conceived to provide a blower fan whichis able to efficiently cool a heat source.

SUMMARY OF THE INVENTION

A blower fan according to a preferred embodiment of the presentinvention includes an impeller, a motor portion, and a housing. Theimpeller includes a plurality of blades and a blade support portion. Theblades are arranged to rotate about a central axis extending in avertical direction, and are arranged in a circumferential direction. Theblade support portion is arranged to support the blades. The motorportion is arranged to rotate the impeller. The housing is arranged tocontain the impeller. The housing includes a lower plate portion and aside wall portion. The lower plate portion is arranged to cover a lowerside of the impeller, is arranged to support the motor portion, and ismade of a material having a thermal conductivity of 1.0 W/(m·K) or more.The side wall portion is arranged to cover a lateral side of theimpeller, is connected with the lower plate portion, and is made of amaterial having a thermal conductivity of 1.0 W/(m·K) or more. A channeljoining a space above the impeller and a space between the impeller andthe lower plate portion to each other in an axial direction is definedbetween adjacent ones of the blades of the impeller. An upper plateportion arranged to cover an upper side of the impeller includes an airinlet. The upper plate portion, the side wall portion, and the lowerplate portion are arranged to together define an air outlet on thelateral side of the impeller. The blower fan further includes a heatsource contact portion with which a heat source is to be in contact, theheat source contact portion being arranged in a surface of the blowerfan which faces away from the impeller. The air outlet is a planeparallel to the central axis, and including one of an edge of the upperplate portion, a pair of edges of the side wall portion, and an edge ofthe lower plate portion that is the closest to the central axis. Theside wall portion includes a tongue portion arranged to project betweenthe air outlet and the impeller. The heat source contact portion and thetongue portion are arranged to at least partially overlap with eachother in the plan view.

The present invention is able to provide a blower fan which is capableof efficiently cooling a heat source.

The above and other features, elements, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of preferred embodiments of the presentinvention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a blower fan according to a firstpreferred embodiment of the present invention.

FIG. 2 is a cross-sectional view of a motor portion and its vicinityaccording to the first preferred embodiment.

FIG. 3 is a cross-sectional view of a sleeve according to the firstpreferred embodiment.

FIG. 4 is a plan view of the sleeve.

FIG. 5 is a bottom view of the sleeve.

FIG. 6 is a cross-sectional view of a bearing portion and its vicinityaccording to the first preferred embodiment.

FIG. 7 is a top view of the blower fan with an upper plate portionremoved therefrom.

FIG. 8 is a top view of a blower fan according to an examplemodification of the first preferred embodiment with an upper plateportion removed therefrom.

FIG. 9 is a cross-sectional view of a portion of a blower fan accordingto another example modification of the first preferred embodiment,illustrating a lower plate portion and its vicinity.

FIG. 10 is a bottom view of a lower plate portion of a blower fanaccording to yet another example modification of the first preferredembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is assumed herein that a vertical direction is defined as a directionin which a central axis of a motor portion extends, and that an upperside and a lower side along the central axis in FIG. 1 are referred tosimply as an upper side and a lower side, respectively. It should benoted, however, that the above definitions of the vertical direction andthe upper and lower sides should not be construed to restrict relativepositions or directions of different members or portions when the motorportion is actually installed in a device. Also note that a directionparallel to the central axis is referred to by the term “axialdirection”, “axial”, or “axially”, that radial directions centered onthe central axis are simply referred to by the term “radial direction”,“radial”, or “radially”, and that a circumferential direction about thecentral axis is simply referred to by the term “circumferentialdirection”, “circumferential”, or “circumferentially”.

FIG. 1 is a cross-sectional view of a blower fan 1 according to a firstpreferred embodiment of the present invention. The blower fan 1according to the present preferred embodiment is a centrifugal fan, andis used, for example, in a notebook personal computer in which a heatsource 30, i.e., a CPU or another electronic component which is anotherheat-radiating component, is arranged directly on the blower fan 1 tocool the CPU or the other electronic component. The blower fan 1includes an impeller 11, a motor portion 12, and a housing 13. Theimpeller 11 is arranged to extend radially outward from a rotatingportion 22 of the motor portion 12. The impeller 11 is caused by themotor portion 12 to rotate about a central axis J1.

The impeller 11 is made of a resin having excellent thermal conductivity(hereinafter referred to as a “heat conductive resin”), and includes aplurality of blades 112 arranged in a circumferential direction, and asubstantially annular blade support portion 111 arranged to support theblades 112. An inner circumferential surface of the blade supportportion 111 is fixed to the rotating portion 22 of the motor portion 12.The blades 112 are arranged to extend radially outward from an outercircumferential surface of the blade support portion 111 with thecentral axis J1 as a center. The blade support portion 111 and theblades 112 are defined as a single continuous member by a resininjection molding process. Note that the impeller 11 may be made ofaluminum. A heat in the heat source 30 is transferred to the impeller 11through the housing 13 and the motor portion 12. Rotation of theimpeller 11 enables dissipation of the heat. In the case where theimpeller 11 is made of the heat conductive resin, the impeller 11 iscapable of rotating at a higher speed, since the heat conductive resinhas a specific gravity smaller than that of aluminum. Air volume isthereby increased, and an improvement in cooling performance isachieved. The heat conductive resin is preferably a resin including ametal filler, and in this case, a further improvement in the coolingperformance is achieved. Note that the impeller 11 is preferablyarranged to have a thermal conductivity of 1.0 W/(m·K) or more. Morepreferably, the impeller 11 is arranged to have a thermal conductivityof 3.0 W/(m·K) or more.

The blower fan 1 is arranged to produce air currents through therotation of the impeller 11 about the central axis J1 caused by themotor portion 12.

The housing 13 is arranged to contain the motor portion 12 and theimpeller 11. The housing 13 includes an upper plate portion 131, amounting plate 132 (hereinafter referred to as a lower plate portion132), and a side wall portion 133. The upper plate portion 131 is asubstantially plate-shaped member made of a metal. The upper plateportion 131 is arranged above the motor portion 12 and the impeller 11to cover an upper side of the impeller 11. The upper plate portion 131includes one air inlet 151 arranged to pass therethrough in a verticaldirection. The air inlet 151 is arranged to axially overlap with atleast a portion of the impeller 11 and the entire motor portion 12. Theair inlet 151 is substantially circular, and the central axis J1 passestherethrough. At least one pair of adjacent ones of the blades 112 arearranged to define a channel therebetween, the channel joining a spaceaxially above the blades 112 and a space between the blades 112 and thelower plate portion 132 to each other in an axial direction. The channelis arranged to be open toward an upper surface of the lower plateportion 132. Thus, an air sucked through the air inlet 151 passesbetween the adjacent blades 112 of the impeller 11 toward the lowerplate portion 132. The lower plate portion 132 and the heat source 30are in thermal contact with each other. The thermal contact between thelower plate portion 132 and the heat source 30 enables a heat to betransferred from the heat source 30 to the lower plate portion 132. Thatis, since the air sucked through the air inlet 151 passes between theadjacent blades 112 of the impeller 11 toward the lower plate portion132, a wind strikes the lower plate portion 132 to achieve animprovement in the cooling performance.

The lower plate portion 132 is a substantially plate-shaped memberproduced by subjecting a metal sheet to press working. The lower plateportion 132 is arranged below the motor portion 12 and the impeller 11to support the motor portion 12. According to the present preferredembodiment, the lower plate portion 132 is made of aluminum. In thiscase, the heat can be dissipated through the lower plate portion 132.Note that a material of the lower plate portion 132 may be copper, analuminum alloy, iron, an iron-base alloy (including SUS), or a heatconductive resin.

The blower fan 1 includes, in a surface thereof facing away from theimpeller 11, a heat source contact portion 10 with which the heat source30 is to be in contact. The heat source 30 is the CPU or the otherelectronic component which is the other heat-radiating component.According to the present preferred embodiment, an upper surface of theheat source 30 is arranged to be in thermal contact with a lower surfaceof the lower plate portion 132. The heat source 30 and the lower plateportion 132 are arranged to be in close contact with each other with aheat-conducting member, such as grease or a thermal sheet which is aportion of the heat source 30, arranged therebetween, and thisheat-conducting member causes the heat source 30 and the lower surfaceof the lower plate portion 132 to be in thermal contact with each other.Note that the heat source contact portion 10 may be arranged at alocation different from the lower plate portion 132, as described below.

The side wall portion 133 is made of a resin. The side wall portion 133is arranged to cover a lateral side of the impeller 11. That is, theside wall portion 133 is arranged radially outside the blades 112 tosurround the blades 112. The upper plate portion 131 is fixed to anupper end portion of the side wall portion 133 through screws or byanother fixing method. A lower end portion of the side wall portion 133is joined to the lower plate portion 132 by an insert molding process.The side wall portion 133 is arranged substantially in the shape of theletter “U” when viewed in a direction parallel to the central axis J1,and includes an air outlet 153 which opens radially outward. In moredetail, portions of the upper and lower plate portions 131 and 132 arearranged on an upper side and a lower side, respectively, of an openingof the side wall portion 133. The air outlet 153 is a plane parallel tothe central axis J1 and including one of an edge of the upper plateportion 131, a pair of edges which are circumferential ends of theopening of the side wall portion 133, and an edge of the lower plateportion 132 that is the closest to the central axis J1. According to thepresent preferred embodiment, an area enclosed by the upper and lowerplate portions 131 and 132 and the opening of the side wall portion 133is the air outlet 153. Note that the side wall portion 133 may notnecessarily be provided by the insert molding process. Also note thatthe side wall portion 133 may not necessarily be made of the resin. Alsonote that each of the upper and lower plate portions 131 and 132 may befixed to the side wall portion 133 by a fixing method not mentionedabove.

FIG. 2 is a cross-sectional view of the motor portion 12 and itsvicinity. The motor portion 12 is of an outer-rotor type. The motorportion 12 includes a stationary portion 21 and the rotating portion 22.The stationary portion 21 includes a bearing portion 23, the lower plateportion 132, a stator 210, and a circuit board 25.

The bearing portion 23 is arranged radially inward of the stator 210.The bearing portion 23 includes a sleeve 231 and a bearing housing 232.The sleeve 231 is substantially cylindrical in shape and centered on thecentral axis J1. The sleeve 231 is a metallic sintered body. The sleeve231 is impregnated with a lubricating oil. A plurality of circulationgrooves 275, each of which is arranged to extend in the axial directionand through each of which the lubricating oil circulates, are defined inan outer circumferential surface of the sleeve 231. The circulationgrooves 275 are arranged at regular intervals in the circumferentialdirection. The bearing housing 232 is substantially cylindrical and hasa bottom, and includes a housing cylindrical portion 241 and a cap 242.The housing cylindrical portion 241 is substantially cylindrical inshape and centered on the central axis J1, and is arranged to cover theouter circumferential surface of the sleeve 231. The sleeve 231 is fixedto an inner circumferential surface of the housing cylindrical portion241 through an adhesive. The bearing housing 232 is made of a metal. Thecap 242 is fixed to a lower end portion of the housing cylindricalportion 241. The cap 242 is arranged to close a bottom portion of thehousing cylindrical portion 241. Note that use of the adhesive to fixthe sleeve 231 to the inner circumferential surface of the housingcylindrical portion 241 is not essential to the present invention. Forexample, the sleeve 231 may be fixed to the inner circumferentialsurface of the housing cylindrical portion 241 through press fit. Notethat each of the sleeve 231, the bearing housing 232, and the cap 242may be made of a nonmetallic material having excellent thermalconductivity. For example, each of the sleeve 231, the bearing housing232, and the cap 242 may be made of a heat conductive resin or brass.

The lower plate portion 132 includes a rising portion 1321 in a radiallyinner portion thereof. The rising portion 1321 is a substantiallyannular portion. A lower region of an outer circumferential surface ofthe housing cylindrical portion 241, i.e., a lower region of an outercircumferential surface of the bearing housing 232, is fixed to an innercircumferential surface of the rising portion 1321 through adhesion orpress fit. Note that both adhesion and press fit may be used to fix thebearing housing 232 and the rising portion 1321 to each other.

The stator 210 is a substantially annular member centered on the centralaxis J1. The stator 210 includes a stator core 211 and a plurality ofcoils 212 arranged on the stator core 211. The stator core 211 isdefined by laminated silicon steel sheets, each of which is in the shapeof a thin sheet. The stator core 211 includes a substantially annularcore back 211 a and a plurality of teeth 211 b arranged to projectradially outward from the core back 211 a. A conducting wire is woundaround each of the teeth 211 b to define the coils 212. The circuitboard 25 is arranged below the stator 210. Lead wires of the coils 212are electrically connected to the circuit board 25. The circuit board 25is a flexible printed circuit (FPC) board.

The rotating portion 22 includes a shaft 221, a thrust plate 224, arotor holder 222, and a rotor magnet 223. The shaft 221 is arranged tohave the central axis J1 as a center thereof.

Referring to FIG. 1, the rotor holder 222 is arranged substantially inthe shape of a covered cylinder and centered on the central axis J1. Therotor holder 222 includes a tubular “cylindrical magnet holding portion”222 a, a cover portion 222 c, and a first thrust portion 222 d. Thecylindrical magnet holding portion 222 a, the cover portion 222 c, andthe first thrust portion 222 d are defined integrally with one another.The first thrust portion 222 d is arranged to extend radially outwardfrom an upper end portion of the shaft 221. The cover portion 222 c isarranged to extend radially outward from the first thrust portion 222 d.The upper plate portion 131 is arranged above the cover portion 222 cand the first thrust portion 222 d. A lower surface of the cover portion222 c is a substantially annular surface arranged around the shaft 221.Referring to FIG. 2, the first thrust portion 222 d is arranged axiallyopposite each of an upper surface 231 b of the sleeve 231 and an uppersurface of the housing cylindrical portion 241.

The thrust plate 224 includes a substantially disk-shaped portionarranged to extend radially outward. The thrust plate 224 is fixed to alower end portion of the shaft 221, and is arranged to extend radiallyoutward from the lower end portion thereof. The thrust plate 224 isaccommodated in a plate accommodating portion 239 defined by a lowersurface 231 c of the sleeve 231, an upper surface of the cap 242, and alower portion of the inner circumferential surface of the housingcylindrical portion 241. An upper surface of the thrust plate 224 is asubstantially annular surface arranged around the shaft 221. The uppersurface of the thrust plate 224 is arranged axially opposite the lowersurface 231 c of the sleeve 231, i.e., a downward facing surface in theplate accommodating portion 239. Hereinafter, the thrust plate 224 willbe referred to as a “second thrust portion 224”. A lower surface of thesecond thrust portion 224 is arranged opposite to the upper surface ofthe cap 242 of the bearing housing 232. The shaft 221 is inserted in thesleeve 231. Note that the thrust plate 224 may be defined integrallywith the shaft 221. The thrust plate 224 is made, for example, of ametal, such as stainless steel.

The shaft 221 is defined integrally with the rotor holder 222. The shaft221 and the rotor holder 222 are produced by subjecting a metallicmember to a cutting process. That is, the cover portion 222 c and theshaft 221 are continuous with each other. Note that the shaft 221 may bedefined by a member separate from the rotor holder 222. In this case,the upper end portion of the shaft 221 is fixed to the cover portion 222c of the rotor holder 222. Referring to FIG. 1, the rotor magnet 223 isfixed to an inner circumferential surface of the cylindrical magnetholding portion 222 a, which is arranged to extend axially downward froma radially outer end portion of the cover portion 222 c of the rotorholder 222. The shaft 221 is made, for example, of a metal, such asstainless steel.

Referring to FIG. 2, the rotor holder 222 further includes asubstantially annular “annular tubular portion” 222 b arranged to extenddownward from an outer edge portion of the first thrust portion 222 d.The annular tubular portion 222 b will be hereinafter referred to as a“rotor cylindrical portion 222 b”. The rotor cylindrical portion 222 bof the rotor holder 222 is arranged radially inward of the stator 210.The rotor cylindrical portion 222 b is arranged radially outward of thebearing housing 232. An inner circumferential surface of the rotorcylindrical portion 222 b is arranged radially opposite an outercircumferential surface of an upper portion of the housing cylindricalportion 241. A seal gap 35 is defined between the inner circumferentialsurface of the rotor cylindrical portion 222 b and the outercircumferential surface of the housing cylindrical portion 241. A sealportion 35 a having a surface of the lubricating oil defined therein isdefined in the seal gap 35.

Referring to FIG. 1, the inner circumferential surface of the bladesupport portion 111 is fixed to an outer circumferential surface of thecylindrical magnet holding portion 222 a of the rotor holder 222. Theblades 112 are arranged outside the outer circumferential surface of thecylindrical magnet holding portion 222 a. The upper end portion of theshaft 221 is fixed to the impeller 11 through the rotor holder 222. Notethat the impeller 11 may be defined integrally with the rotor holder222. In this case, the upper end portion of the shaft 221 is fixed tothe impeller 11 in a direct manner.

The rotor magnet 223 is substantially cylindrical in shape and centeredon the central axis J1. As described above, the rotor magnet 223 isfixed to the inner circumferential surface of the cylindrical magnetholding portion 222 a. The rotor magnet 223 is arranged radially outsidethe stator 210.

Referring to FIG. 2, the rising portion 1321 includes a rising uppertubular portion 1321 a arranged to project upward at an upper endthereof. An outer circumferential surface of the rotor cylindricalportion 222 b is arranged opposite to an inner circumferential surfaceof the rising upper tubular portion 1321 a with a radial gap(hereinafter referred to as a minute gap 231 d) interveningtherebetween. Entrance and exit of a gas through this minute gap 231 dare limited. This contributes to reducing evaporation of the lubricatingoil through the seal portion 35 a. The radial width of the minute gap231 d is arranged to be 0.15 mm or less than 0.15 mm. More preferably,the radial width of the minute gap 231 d is arranged to be 0.10 mm orless than 0.10 mm.

FIG. 3 is a cross-sectional view of the sleeve 231. A first radialdynamic pressure groove array 271 and a second radial dynamic pressuregroove array 272 are defined in an upper portion and a lower portion,respectively, of an inner circumferential surface 231 a of the sleeve231. Each of the first and second radial dynamic pressure groove arrays271 and 272 is made up of a plurality of grooves arranged in aherringbone pattern. FIG. 4 is a plan view of the sleeve 231. A firstthrust dynamic pressure groove array 273 is defined in the upper surface231 b of the sleeve 231. The first thrust dynamic pressure groove array273 is made up of a plurality of grooves arranged in a spiral pattern.FIG. 5 is a bottom view of the sleeve 231. A second thrust dynamicpressure groove array 274 is defined in the lower surface 231 c of thesleeve 231. The second thrust dynamic pressure groove array 274 is madeup of a plurality of grooves arranged in the spiral pattern.

FIG. 6 is a cross-sectional view of the bearing portion 23 and itsvicinity. A radial gap 31 is defined between an outer circumferentialsurface of the shaft 221 and the inner circumferential surface 231 a ofthe sleeve 231. The radial gap 31 includes a first radial gap 311 and asecond radial gap 312, which is arranged on a lower side of the firstradial gap 311. The first radial gap 311 is defined between the outercircumferential surface of the shaft 221 and a portion of the innercircumferential surface 231 a of the sleeve 231 in which the firstradial dynamic pressure groove array 271 illustrated in FIG. 3 isdefined. The lubricating oil is arranged in the first radial gap 311.The second radial gap 312 is defined between the outer circumferentialsurface of the shaft 221 and a portion of the inner circumferentialsurface 231 a of the sleeve 231 in which the second radial dynamicpressure groove array 272 illustrated in FIG. 3 is defined. Thelubricating oil is arranged in the second radial gap 312. The first andsecond radial gaps 311 and 312 are arranged to together define a radialdynamic pressure bearing portion 31 a arranged to produce a fluiddynamic pressure in the lubricating oil. The shaft 221 is supported in aradial direction by the radial dynamic pressure bearing portion 31 a.The radial width of the radial gap 31 is arranged to be 5 μm or lessthan 5 μm. More preferably, the radial width of the radial gap 31 isarranged to be 3 μm or less than 3 μm.

A thrust portion (not shown) includes the first thrust portion 222 d,which is an upper thrust portion, and the second thrust portion 224,which is a lower thrust portion. A first thrust gap 34 is definedbetween a portion of the upper surface 231 b of the sleeve 231 in whichthe first thrust dynamic pressure groove array 273 is defined and alower surface of the first thrust portion 222 d. The lubricating oil isarranged in the first thrust gap 34. The first thrust gap 34 is arrangedto define an upper thrust dynamic pressure bearing portion 34 a arrangedto produce a fluid dynamic pressure in the lubricating oil. The firstthrust portion 222 d is supported in the axial direction by the upperthrust dynamic pressure bearing portion 34 a. The axial width of thefirst thrust gap 34 is arranged to be 70 μm or less than 70 μm. Morepreferably, the axial width of the first thrust gap 34 is arranged to be45 μm or less than 45 μm.

A second thrust gap 32 is defined between a portion of the lower surface231 c of the sleeve 231 in which the second thrust dynamic pressuregroove array 274 is defined and the upper surface of the second thrustportion 224. The lubricating oil is arranged in the second thrust gap32. The second thrust gap 32 is arranged to define a lower thrustdynamic pressure bearing portion 32 a arranged to produce a fluiddynamic pressure in the lubricating oil. The second thrust portion 224is supported in the axial direction by the lower thrust dynamic pressurebearing portion 32 a. The upper and lower thrust dynamic pressurebearing portions 34 a and 32 a are arranged to be in communication witheach other through the circulation grooves 275.

A third thrust gap 33 is defined between the upper surface of the cap242 of the bearing housing 232 and the lower surface of the secondthrust portion 224. The third thrust gap 33 may be arranged to produce afluid dynamic pressure in the lubricating oil between the upper surfaceof the cap 242 and the lower surface of the second thrust portion 224.

In the motor portion 12, the seal gap 35, the first thrust gap 34, theradial gap 31, the second thrust gap 32, and the third thrust gap 33 arearranged to together define a single continuous bladder structure, andthe lubricating oil is arranged continuously in this bladder structure.Within the bladder structure, a surface of the lubricating oil isdefined only in the seal gap 35.

Referring to FIG. 2, in the motor portion 12, the shaft 221, the firstthrust portion 222 d, the rotor cylindrical portion 222 b, which isarranged to extend downward from the outer edge portion of the firstthrust portion 222 d, the second thrust portion 224, the bearing portion23, the rising portion 1321, and the lubricating oil are arranged totogether define a bearing mechanism 4, which is a bearing apparatus.Hereinafter, each of the shaft 221, the first thrust portion 222 d, therotor cylindrical portion 222 b, the second thrust portion 224, thebearing portion 23, and the rising portion 1321 will be referred to as aportion of the bearing mechanism 4. In the bearing mechanism 4, theshaft 221, the first thrust portion 222 d, and the second thrust portion224 are arranged to rotate relative to the bearing portion 23 with thelubricating oil intervening therebetween.

In the motor portion 12, once power is supplied to the stator 210, atorque centered on the central axis J1 is produced between the rotormagnet 223 and the stator 210. The rotating portion 22 and the impeller11 are supported through the bearing mechanism 4 illustrated in FIG. 2such that the rotating portion 22 and the impeller 11 are rotatableabout the central axis J1 with respect to the stationary portion 21. Therotation of the impeller 11 causes an air to be drawn into the housing13 through the air inlet 151 and then sent out through the air outlet153.

FIG. 7 is a top view of the blower fan 1 with the upper plate portion131 removed therefrom. The heat source contact portion 10 and the sidewall portion 133 are arranged to at least partially overlap with eachother in a plan view. This enables a heat originating from the heatsource 30 to be efficiently transferred to both the side wall portion133 and the lower plate portion 132. There are two air currents causedby the rotation of the impeller 11. A first air current is an aircurrent which flows in the circumferential direction from the tongueportion 134 toward the air outlet 153 as described above. A second aircurrent is an air current which flows radially from the air inlet 151toward the side wall portion 133 along the blades 112. Regarding thesecond air current, since the circumferential velocity of each blade 112increases with increasing distance from the central axis J1, an aircurrent around the impeller 11 becomes fastest at a radially outer end,that is, in the vicinity of the side wall portion 133. That is, aneffect of forced cooling caused by the air current is greatest in thevicinity of a radially outermost end of the lower plate portion 132 andthe side wall portion 133. Therefore, a heat which is present at each ofthe radially outermost end of the lower plate portion 132 and an innercircumferential surface of the side wall portion 133 can be efficientlydischarged. In addition, each of the lower plate portion 132 and theside wall portion 133 is made of a material having a thermalconductivity of 1.0 W/(m·K) or more. When each of the side wall portion133 and the lower plate portion 132 is made of a material having a highthermal conductivity, a surface area through which the heat can bedissipated is increased in the vicinity of the radially outermost end ofthe lower plate portion 132 and the side wall portion 133, where theflow velocity of the air current is high. Accordingly, an improvement inheat dissipation performance is achieved.

A portion of the heat source contact portion 10 is arranged radiallyinward of the inner circumferential surface of the side wall portion 133in the plan view. When a portion of the heat source contact portion 10is arranged radially inward of the inner circumferential surface of theside wall portion 133, a heat is transferred from the heat source 30 tothe lower plate portion 132, and the temperature of the lower plateportion 132 is increased. As mentioned above, the flow velocity of theair current caused by the rotation of the impeller 11 is highest in aregion in the vicinity of the radially outermost end of the lower plateportion 132 and the side wall portion 133. Since an air current having ahigh flow velocity impinges on the region in the vicinity of theradially outermost end of the lower plate portion 132 and the side wallportion 133, a heat transferred to each of the lower plate portion 132and the side wall portion 133 is dissipated with increased efficiency.Note that, in the case where the entire heat source 30 cannot bearranged in a region inside an outer circumference of the side wallportion 133 because, for example, another electronic component isarranged under the lower plate portion 132, a portion of the heat sourcecontact portion 10 may be arranged radially outward of the outercircumference of the side wall portion 133.

The area of a region over which the heat source contact portion 10 andthe side wall portion 133 overlap with each other in the plan view isarranged to be smaller than the area of a region of the heat sourcecontact portion 10 radially inside the inner circumferential surface ofthe side wall portion 133. In this case, a heat is more easilytransferred from the heat source 30 to the lower plate portion 132 thanin the case where the entire heat source 30 is arranged on a lowersurface of the side wall portion 133. That is, the surface area throughwhich the heat can be dissipated can be increased in the vicinity of theradially outermost end of the lower plate portion 132 and the side wallportion 133, where the flow velocity of the air current is high, byincreasing the area of a region over which the heat source contactportion 10 axially overlaps with the lower plate portion 132.Accordingly, a further improvement in the heat dissipation performanceis achieved.

Further, in the plan view, an imaginary straight line which is parallelto the air outlet 153 and which intersects with the central axis J1 isdefined as a first imaginary straight line 41, and an imaginary straightline which is perpendicular to the air outlet 153 and which intersectswith the central axis J1 is defined as a second imaginary straight line42. Of four regions divided by the first and second imaginary straightlines 41 and 42, a region in which the tongue portion 134 is arranged isdefined as a first region 51, and the three other regions are defined asa second region 52, a third region 53, and a fourth region 54 in anorder in which the three regions are arranged in a rotation direction ofthe impeller 11 from the first region 51. In this case, the heat sourcecontact portion 10 is arranged in the fourth region 54. As mentionedabove, the rotation of the impeller 11 of the blower fan 1 causes an airto flow downstream along the rotation direction of the impeller 11. Atthis time, the tongue portion 134 is at an upstream end, and the airoutlet 153 is at a downstream end. Regarding the blower fan 1, as theair current travels downstream, the flow velocity of the air currentincreases, and the amount of heat carried thereby also increases. Here,since the heat source contact portion 10 is arranged in the fourthregion 54, the temperature of the lower plate portion 132 is increasedin the fourth region 54. Meanwhile, in an entire region outside thefourth region 54, the temperature of the lower plate portion 132 is low,and accordingly, the temperature of an air current passing therein islow. The entire region outside the fourth region 54 is an upstreamregion in which the tongue portion 134 is arranged, and the air currenthaving a low temperature will pass the fourth region 54. Accordingly,arrangement of the heat source contact portion 10 in the fourth region54 makes it possible to reduce the temperature of the air currentpassing the fourth region 54, and leads to an improvement in the coolingperformance.

The heat source contact portion 10 and the blades 112 are arranged to atleast partially overlap with each other in the plan view. A regionradially outside an outer circumference of the blade support portion 111is a region in which air currents caused by the rotation of the impeller11 flow. An air sucked through the air inlet 151 passes between theadjacent blades 112 of the impeller 11 toward the lower plate portion132. Thus, when the heat source contact portion 10 is arranged toaxially overlap with the blades 112, an improvement in the coolingperformance is achieved.

FIG. 8 is a top view of a blower fan according to an examplemodification of the above-described preferred embodiment with an upperplate portion 131 removed therefrom. A side wall portion 133 includes atongue portion 134 arranged to project between an air outlet 153 and animpeller 11. A heat source contact portion 10 and the tongue portion 134may be arranged to at least partially overlap with each in a plan view.The tongue portion 134 is greater in volume than a remaining portion ofthe side wall portion 133. Improvements in heat transfer performance andthe cooling performance can be achieved by increasing the area of aregion over which the heat source contact portion 10 and the tongueportion 134 axially overlap with each other.

FIG. 9 is a cross-sectional view of a blower fan 1 b according toanother example modification of the above-described preferredembodiment, illustrating a lower plate portion 132 b and its vicinity.The basic structure of the blower fan 1 b according to the presentexample modification is similar to that of the blower fan 1 according tothe above-described preferred embodiment. According to the presentexample modification, the lower plate portion 132 b and a side wallportion 133 b are defined by a single member. When the lower plateportion 132 b and the side wall portion 133 b are defined by the singlemember, a heat dissipated from a heat source (not shown) is moreefficiently transferred to both the lower plate portion 132 b and theside wall portion 133 b. The flow velocity of an air current is high ata radially outermost end of the lower plate portion 132 b and an innercircumferential surface of the side wall portion 133 b, and heat insurfaces of the lower plate portion 132 b and the side wall portion 133b can be efficiently discharged by winds caused by an impeller 11 bstriking the radially outermost end of the lower plate portion 132 b andthe inner circumferential surface of the side wall portion 133 b.

Note that the lower plate portion 132 b and the side wall portion 133 bmay be made of a heat conductive resin and a metal, respectively, andthe lower plate portion 132 b and the side wall portion 133 b may beintegrally defined by an insert molding process. When the lower plateportion 132 b is made of the resin, the lower plate portion 132 b can bearranged to have a complicated shape, and a reduction in a productioncost is achieved.

FIG. 10 is a bottom view of a lower plate portion 132 c of a blower fan1 c according to yet another example modification of the above-describedpreferred embodiment. The basic structure of the blower fan 1 caccording to the present example modification is similar to that of theblower fan 1 according to the above-described preferred embodiment. Thelower plate portion 132 c includes, in a lower surface thereof, a heatsource accommodating portion 50 c arranged to accommodate a heat source30 c. Inclusion of the heat source accommodating portion 50 c in thelower plate portion 132 c facilitates positioning of the heat source 30c and the blower fan 1 c relative to each other. Note that, although theheat source accommodating portion 50 c is defined by a portion of thelower surface of the lower plate portion 132 c being recessed axiallyupward in the present example modification, this is not essential to thepresent invention. For example, a portion of the lower plate portion 132c, which is defined in the shape of a plate, may be arranged to projectaxially upward to define the heat source accommodating portion 50 c.Note that at least a portion of the heat source accommodating portion 50c is preferably arranged in a region between outer circumferential endsof a plurality of blades 112 c and an outer circumferential end of ablade support portion 111 c. When at least a portion of the heat sourceaccommodating portion 50 c is arranged in the region between the outercircumferential ends of the blades 112 c and the outer circumferentialend of the blade support portion 111 c, an air sucked through an airinlet 151 passes between adjacent ones of the blades 112 c of theimpeller 11 c toward the lower plate portion 132 c. When the heat source30 c is arranged under the blades 112 c, a wind strikes a heat sourcecontact portion 10 c to improve cooling performance. Note that, in FIG.10, the blades 112 c and the blade support portion 111 c are representedby imaginary lines.

Note that the blower fan 1 may be modified in a variety of manners.

Note that the blades 112 may not necessarily be arranged at regularintervals but may be arranged at irregular intervals. Also note that twoor more channels having mutually different circumferential widths may beprovided.

Note that motors according to preferred embodiments of the presentinvention may be either of a rotating-shaft type or of a fixed-shafttype. Also note that motors according to preferred embodiments of thepresent invention may be either of the outer-rotor type or of aninner-rotor type.

Note that, in the bearing mechanism 4, only at least one of the upperand lower thrust dynamic pressure bearing portions may be definedwithout any radial dynamic pressure bearing portion being defined.

Note that the bearing housing 232 may not necessarily be made up of thehousing cylindrical portion 241 and the cap 242, but may be defined by asingle member being substantially cylindrical and having a bottom.

Note that the lower plate portion 132 and the rising portion 1321 may bedefined by separate members. In this case, an outer circumferentialsurface of the rising portion 1321 is fixed to a hole portion of thelower plate portion 132. The rising portion 1321 is produced bysubjecting a metallic member to a cutting process. Note that the risingportion 1321 may be made of a nonmetallic material. For example, therising portion 1321 may be made of a heat conductive resin.

Note that, in the blower fan 1, the air inlet 151 may be defined in onlyone of the upper and lower plate portions 131 and 132. In other words,regarding the blower fan 1, it is enough that the upper plate portion131 or the lower plate portion 132 should include the air inlet 151.Also note that, in the blower fan 1, the upper plate portion 131 may beomitted from the housing 13. In this case, the upper end portion of theside wall portion 133 is fixed to a case of the notebook PC in which theblower fan 1 is installed, and the upper side of the impeller 11 iscovered with this case. That is, a portion of the case of the notebookPC is arranged to define the upper plate portion 131. In other words,the case of the notebook PC includes a top plate arranged to cover anupper side of the blower fan 1 as a substitute for the upper plateportion 131 of the blower fan 1, a side plate arranged on a lateral sideof the blower fan 1, and a bottom plate arranged below the blower fan 1,and the top plate includes the air inlet 151. An electronic deviceincluding the blower fan 1 as described above is able to efficientlyreduce heat generated from the heat source 30 so that performance of theelectronic device can be maintained and a long life of the electronicdevice can be achieved.

Blower fans according to preferred embodiments of the present inventionare usable to cool devices inside cases of notebook PCs and desktop PCs,to cool other devices, to supply an air to a variety of objects, and soon. Moreover, blower fans according to preferred embodiments of thepresent invention are also usable for other purposes.

The preferred embodiments of the present invention and modificationsthereof are applicable to spindle motors and disk drive apparatuses.

Features of the above-described preferred embodiments and themodifications thereof may be combined appropriately as long as noconflict arises.

While preferred embodiments of the present invention and modificationsthereof have been described above, it is to be understood thatadditional variations and modifications will be apparent to thoseskilled in the art without departing from the scope and spirit of thepresent invention. The scope of the present invention, therefore, is tobe determined solely by the following claims.

What is claimed is:
 1. A blower fan comprising: an impeller including aplurality of blades arranged to rotate about a central axis extending ina vertical direction and arranged in a circumferential direction, and ablade support portion arranged to support the blades; a motor portionarranged to rotate the impeller; and a housing arranged to contain theimpeller; wherein the housing includes: a lower plate portion arrangedto cover a lower side of the impeller, arranged to support the motorportion, and made of a material having a thermal conductivity of 1.0W/(m·K) or more; and a side wall portion arranged to cover a lateralside of the impeller, connected with the lower plate portion, and madeof a material having a thermal conductivity of 1.0 W/(m·K) or more; achannel joining a space above the impeller and a space between theimpeller and the lower plate portion to each other in an axial directionis defined between adjacent ones of the blades of the impeller; an upperplate portion arranged to cover an upper side of the impeller includesan air inlet; the upper plate portion, the side wall portion, and thelower plate portion are arranged to together define an air outlet on thelateral side of the impeller; the blower fan further comprises a heatsource contact portion with which a heat source is to be in directcontact, the heat source contact portion being arranged in a surface ofthe lower plate portion which faces away from the impeller; the airoutlet is a plane parallel to the central axis, and including one of anedge of the upper plate portion, a pair of edges of the side wallportion, and an edge of the lower plate portion that is the closest tothe central axis; and the side wall portion includes a tongue portionarranged to project between the air outlet and the impeller; and theheat source contact portion and the tongue portion are arranged to atleast partially overlap with each other in the plan view.
 2. The blowerfan according to claim 1, wherein a portion of the heat source contactportion is arranged radially inward of an inner circumferential surfaceof the tongue portion in the plan view.
 3. The blower fan according toclaim 1, wherein an area of a region over which the heat source contactportion and the tongue portion are arranged to overlap with each otherin the plan view is arranged to be greater than an area of a region ofthe heat source contact portion radially inside the innercircumferential surface of the tongue portion.
 4. The blower fanaccording to claim 1, wherein the heat source contact portion and theblades are arranged to at least partially overlap with each other in theplan view.
 5. The blower fan according to claim 1, wherein a sidewallportion and the tongue portion are defined integrally with each other.6. The blower fan according to claim 1, wherein the lower plate portionand the side wall portion are defined integrally with each other.
 7. Anelectronic device comprising: a case; and the blower fan of claim 1;wherein the case includes: a top plate arranged to cover an upper sideof the blower fan as a substitute for the upper plate portion of theblower fan; a side plate arranged on a lateral side of the blower fan;and a bottom plate arranged below the blower fan; and the top plateincludes the air inlet.
 8. The blower fan according to claim 1, whereinthe air inlet being a single air inlet provided in the blower fan,wherein the heat source contact portion and the tongue portion arearranged to at least partially overlap with each other in the plan viewsuch that air is sucked from the single air inlet to cool the lowerplate portion and is exhausted from the air outlet in thecircumferential direction.